I read the post you suggested and I ran Ubuntu from a usb drive - couldn't find any evidence of my D drive through Ubuntu.
After rebooting in Windows as normal, I went to 'Disc Manager' and now there is nothing at all - not only is my D drive missing, but the letterless EISA drive that appeared after the accident is gone as well. All that's showing is my C drive.
I put in the Acer recovery discs - and as soon tried to run the restore I got an error message that restoration had failed and the the system automatically restarted.
So - at present there is no sign of my internal D drive, it has vanished totally and a can't use the recovery discs.
I'm desperate for any help now,